The present disclosure relates to wind turbines. More particularly, it relates to off-shore wind turbines and methods for installing off-shore wind turbines.
Due to limited availability of suitable areas for wind turbines on land, the concept of off-shore wind energy production has gained importance in recent years. In shallow coastal waters, wind turbines are usually mounted on concrete foundations on the sea bed, whereas in deeper waters, the turbines may be fixed via chains, cables, lines or moorings to the sea bed.
Off-shore towers and foundations are available in many sorts. For water depths over 30 meters, a jacket type is chosen in many cases. In many cases, a jacket includes multiple legs joining around or above the waterline, often interconnected via cross members. The transition from the jacket to the main tower is often made just above the highest wave height, well below the height of the blade-tip in its lowest position.
The installation of off-shore wind turbines is critical. Off-shore wind turbines require weather windows in which the weather conditions allow assembly of the wind turbines at sea. In particular, the wave height and the resulting motion of the boats and ships present is an important factor for the set up and erection of off-shore wind turbines. For instance, some off-shore turbine installation techniques require the wave height to be below 1 m or maximally 2 m. Further, when installing large turbines, prior art techniques require the provision of hydraulic buffers and/or heavy transition segments with damping cylinders attached. This is voluminous, inefficient, and expensive.
The lower the weather condition requirements, the larger the weather windows that allow the set up. Further, the less amount of work that has to be done at sea, the more work can be done in those periods and the faster the wind turbine can be put into operation.
In summation, in order to erect an off-shore wind turbine one has to bring together large components in a hostile environment. In light of the above, it is desirable to have a wind turbine erection method for off-shore use that allows an easier set up under non-perfect weather conditions.